in 3.0 plans there no user roaming data so no cost to you (note republic still uses some data for call routing and texts so roaming data needs to be left on)
for 2.0 refund plans roaming data is 18.3x the cost native or about 27 cents per MB or $276 per GB

Simple answer is that there are no separate roaming charges that will show up at the end of the month on top of your monthly bill. Here are some additional details regarding roaming Roaming is included for Calls and Text. There is no roaming data and therefore no roaming charges on the Clear Choice Plans. The legacy 2.0 Refund plans include access to roaming data that is deducted at 18.3x native cellular data.